Power switches such as insulated-gate bipolar transistors (IGBTs) can be used for many high voltage applications. The gates of the IGBTs can be driven by means of a respective gate unit. When the IGBTs are used e.g. as part of an inverter, by using pulse width modulation (PWM) the IGBTs are continually switched on and off to achieve a sinusoidal waveform. When the IGBTs are off (blocking), the voltage across the IGBT can be used to power the gate unit. Power can be stored between switches e.g. in capacitors to ensure the gate unit is continuously powered.
However, when the IGBTs are used in an application where the IGBTs are conducting during a majority of the time, such as for a DC breaker, there is no reliable reoccurring time when the IGBTs are blocking, to charge up energy to power the gate unit. Nevertheless, it is useful if the power supply can be powered by the main circuit through the IGBTs, to reduce the need for any external power source.
Consequently, there is a need to provide a power supply for providing power to control a power switch which does not require the power switch to be blocking to function.